Function allocator_init

runtime/dfsan/taint_allocator.cpp:20–24

 */

void allocator_init(uptr begin, uptr end) {
  begin_addr = begin;
  atomic_store_relaxed(&next_usable_byte, begin);
  end_addr = end;
}

void *allocator_alloc(uptr size) {
  if (begin_addr == 0) {